Stabilization of citrus concentrates with fumaric acid or its salts



United States Patent STABILIZATION 0F CITRUS CONCENTRATES WITH FUMARIC ACID OR ITS SALTS Robert J. McColloch, Pasadena, and Bruno Gentili, Glendale, Calif., assignors to the United States of America as represented by the Secretary of Agriculture No Drawing. Application July 11, 1956 Serial No. 597,306

6 Claims. (Cl. 99155) (Granted under Title 35, U. S. Code (1952), see. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, throughout the world for all purposes of the United States government, with the power to grant sub-licenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates in general to the production of stabilized citrus juice concentrates. A particular object of the invention is the provision of citrus juice concentrates which can be stored without cloud loss. Another object of the invention is the provision of methods for producing such stabilized concentrates. Further objects and advantages of the invention will be obvious from the description herein.

It is well known in the art that freshly prepared citrus juices are not clear but contain a cloud of pulp and colloidal material suspended in the juice serum. It is generally recognized that most of the flavor is associated with the cloud material rather than with the clear serum. It is obvious that to receive consumer acceptance, a concentrated citrus juice product must form a reconstituted juice having the characteristic cloud of the freshly prepared uice.

At the present time, citrus juices are preserved on a large scale in the form of 4-fold (42 Brix) frozen concentrates. Although these products have received wide acceptance, there is one problem that has always beset the industry. This problem concerns the fact that on storage the concentrates tend to lose their cloud (the suspended pulp tends to clot and settle out). This detrimental effect is accelerated by increased storage temperature. The effect of temperature on the cloud stability of unheated orange juice concentrate is illustrated by the following table:

The changes in the nature of the concentrate illustrated above are deleterious because the concentrate will no longer produce a reconstituted juice with a characteristic cloud. Thus the reconstituted juice will have, a curdy appearance and pulp will settle out rapidly when the juice is not kept agitated, leaving a relatively clear supernatant liquid.

Since cloud loss is generally believed to be the result of pectic enzyme activity on the natural pectin in the juice, heat treatment (pasteurization) of the juice is employed commercially to inactivate the pectic enzymes in order to prevent or inhibit cloud loss and gelation. However, such heat treatment does not necessarily prevent cloud loss even when pectic enzymes appear to be completely inactivated. In addition, heat treatments necessary to completely inactivate the pectic enzymes result in the development of cooked" or other off-flavors in the concentrate.

It has now been found that cloud loss can be greatly inhibited by adding to the concentrate a minor amount of fumaric acid or non-toxic salts thereof. The effect of these compounds on the stability of the concentrate is demonstrated in the examples below. The reason why fumaric acid and its salts possess the ability to stabilize the concentrate is not known. From a practical standpoint, however,-it has been found that they are eifective in this regard. It may also be noted that this activity of furnaric acid and its salts is unique; other polycarboxylic acids which we have tested exhibit no stabilizing effect and indeed some of them, notably malic acid, will accelerate cloud loss.

The invention is further demonstrated by the following illustrative examples.

EXAMPLE I A supply of unheated 4-fold orange juice concentrate Was divided into a series of samples. To these samples was added fumaric acid .or disodium fumarate in the proportions given below. The samples of concentrate containing the additives and a sample of the original concentrate (control) were then stored at 86 F. This storage temperature was used as representing accelerated deleterious conditions since it has been found that in general one hour of storage at 86 F. produces approximately the cloud loss which will occur in 12 to 24 hours at 40f F. It is obvious that in actual use of the process of the invention the product would be stored at a temperature of about 0 F. as is conventional in the storage of frozen citrus concentrates. I

After varying periods of storage, the samples of concentrate were removed from storage'and reconstituted juices prepared therefrom and the cloud in the reconstituted juice measured. made by centrifuging a sample of reconstituted juice for 15 minutes at 2,000 R. P. M. and the turbidity of the supernatant liquid was then determined with a photometric colorimeter using a red #66 filter. Such measurements made on the concentrates before and after storage were used to calculate the percentage of cloud retained by each sample. For instance, if the colorimeter readings on the unstored and stored products are 370 and 285, respectively, then percentage of cloud retained in the stored product is 77%.

The results obtained are tabulated below:

TABLE 2 Inhibition of cloud loss by'added fumarate in unheated orange concentrate held at 86 F.

Proportion Percentage of of additive cloud retained based on after storage Expt. No. Additive weight of for concentrate,

percent 2hours 4hours none (control) none 60 20 fumarie acid. 0. 29 67 39 do 0.58 69 42 disodium fumarate- 0. 40 79 48 5 i o. 0. 80 8t 59 EXAMPLE II The experimentsv set forth in Example I were repeated except that in this case the concentrate was heated for The cloud measurements were 3 1 second at 150 F. before addition of the additives. The results obtained are tabulated below:

' TABLE 3 Inhibition of cloud loss by added fumarate in heat-treated (1 sec. at 150 F.) orange concentrate held at 86 F.

EXAMPLE III The experiments set forth in Example I were repeated except that in this case the concentrate samples, with and without additives, were stored at 40 F. The results obtained are tabulated below:

TABLE 4 Inhibition of cloud loss by added fumarate in unheated orange concentrate held at 40 F.

Proportion Percentage of cloud reof additive tained after storage for Expt. Additive based on No. weight of concentrate, 1 2 3 4 percent day days days days 11 none (control) none 39 20 11 8 12-- tumaric acid 0. 29 61 43 32 19 13 0. 58 82 61 35 26 0. 40 90 69 57 43 0. 80 90 77 63 EXAMPLE IV The experiments set forth in Example I were repeated except that in this case the concentrate was heated for 1 second at 150 F. before addition of the additives. Also, the concentrate samples, with and without additives,

were stored at 40 F. The results obtained are tabulated below:

TABLE Inhibition of cloud loss by added fumarate in heat-treated (1 sec. at 450 F.) orange concentrate held at 40 F.

Proportion Percentage of cloud reof additive tained after storage for- Expt Additive based on No. weight; of

concentrate, 3 5 6 7 percent days days days days 16 none (control) none 65 37 24 11 17 tmnaric acid 0. 29 72 46 38 31 18 do 0. 58 86 56 49 43 19 disodium tumarate.- 0. 40 87 84 79 74 20 do 0. 80 93 91 88 82 As demonstrated above, the stability of citrus concentrates is drastically increased by addition of fumaric acid, or more preferably the non-toxic salts thereof. The salts may be those in which one or both carboxyl groups of the fumaric acid are salified with such cations as sodium, potassium, ammonium, etc. The proportion of fumtlric acid or fumarate to be used depends on the nature of the concentrate and in germral may be about from 0.05 to 0.5%, based on the weight of the reconstituted juice. In adding the fumaric acid orfumarate to the concentrate, one must take into account the fold of the concentrate. For example, if the aim is to use 0.1% based on the reconstituted juice, and the concentrate is of 4-f0ld concentration, one would add about 0.4% of the fumaric acid (or fumarate) to the concentrate.

The preparation of the citrus juice concentrate is not a part of this invention and this material may be prepared from the juices of oranges, grapefruit, lemons, tangerines, etc. by any of the known methods. One common method involves evaporating single-strength citrus juice to a concentration of about 6-fold using evaporation under vacuum to prevent damage to the flavor and color of the juice. The resulting 6-fold concentrate is then cut back with single strength juice to restore flavor and to present a composite concentrate of 4-fold concentration. Instead of restoring flavor by addition of single-strength juice, one can accomplish this end by adding cold-pressed orange peel oil or puree of whole oranges as disclosed in the copending application of R. G. Rice et 211., Serial No. 354,666, filed May 12, 1953. In this case the use of these potent flavor-restoring materials avoids dilution of the concentrate so that the juice can be directly brought to the approximate concentration level intended for ultimate use. In general, the concentrates treated in accordance with the invention may have a concentration from about 2-fold up to 8-fold, or higher. After addition of the fumaric acid or fumarate, the treated concentrate is packaged in the usual way, frozen and maintained under freezing conditions until ready to be used.

It may be noted that the minor amounts of fumaric acid or fumarate do not perceptibly alter the color, taste, odor, or nutritive properties of the juice concentrate.

To get a maximum cloud stabilizing eflfect it is preferable to subject the concentrate, before or after addition of the fumaric acid (or fumarate), to what may be termed a mild heat treatment. This heat treatment is to be distinguished from the severe heating commonly employed in the industry to get cloud stabilization. In accordance with this invention, the mild heat treatment involves applying a temperature of about -180 F. for a period of about 1 to 5 seconds, the shorter time being associated with the higher temperature in the above range, and vice versa. Such heat treatment causes no detectable change in color, flavor, or nutritive quality of the juice. It may also be noted that this mild heat treatment in itself would be insuflicient to impart stability to the concentrate but in combination with the addition of fumaric acid (or fumarate) the concentrate is given a high degree of stability. This aspect of the invention is particularly demonstrated in Examples H and IV, above.

Having thus described the invention, we claim:

1. The method of increasing the cloud stability of a citrus juice concentrate which comprises incorporating into a 4- to 8-fold citrus juice concentrate solely about from 0.05 to 0.5%, based on the weight of the reconstituted juice, of an additive selected from the group consisting of fumaric acid and the non-toxic salts thereof, packaging and freezing the concentrate containing incorporated additive, and maintaining it under freezing conditions, at about 0 F., until it is to be used.

2. The method of claim 1 wherein the additive is fumaric acid.

3. Themethod of claim 1 wherein the additive is disodium fumarate. I

4. The method of increasing the cloud stability of a citrus juice concentrate which comprises subjecting a 4- 'to 8-fold citrus juice concentrate to a mild heat treatment, at about 140-180 F. for a period of about 1 to 5'seconds, which is in itself insufficient to elfectuate a significant cloud stabilization, incorporating into the concentrate solely about from 0.05 to 0.5%, based on the weight of the reeconstituted juice, of an additive selected References Cited in the file of this patent from the group consisting of fumaric acid and the nontoxic salts thereof, packaging and freezing the concen- UNITED STATES PATENTS trate containing incorporated additive, and maintaining 2,622,032 Frandsen 16,1952 o teullllsial: freezing conditions, at about 0 F., until 1t 1s to 5 OTHER REFERENCES 5. The method of claim 4 wherein the additive is fu- Textbook Uses and Applications of Chemicals and maric acid. Related Materials, vol. II, by Thomas C. Gregory.

6. The method of claim 4 wherein the additive is di- Copyright 1944 by Reinhold Publishing Corp., New York, sodium fumarate. 10 New York, page 147. 

1. THE METHOD OF INCREASING THE CLOUD STABILITY OF A CITRUS JUICE CONCENTRATE WHICH COMPRISES INCORPORATING INTO A 4- TO 8-FOLD CITRUS JUICE CONCENTRATE SOLELY ABOUT FROM 0.05 TO 0.5%, BASED ON THE WEIGHT OF THE RECONSTITUTED JUICE, OF AN ADDITIVE SELECTED FROM THE GROUP CONSISTING OF FUMARIC ACID AND THE NON-TOXIC SALTS THEREOF, PACKAGING AND FREEZING THE CONCENTRATE CONTAINING INCORPORATED ADDITIVE, AND MAINTAINING IT UNDER FREEZING CONDITIONS, AT ABOUT 0*F., UNTIL IT IS TO BE USED. 